This invention relates to a sound field control device for realizing presence of a movie in the home and, more particularly, to a sound field control device of this type capable of realizing a surround effect which was not obtainable in prior art surround effect devices.
For realizing presence of a movie in the home, audio and visual devices nowadays tend to have a sound field control device.
In the past, various surround systems have been realized such, for example, as a so-called surround processor according to which sound field components (e.g., reverberation components) contained in a source signal are extracted and emphasized and provided as a surround signal, and the Dolby Surround (trademark) system which inputs a 2-channel source signal and decodes and reproduces from this 2-channel source signal signals of Left, Right and Surround channels and the Dolby Prologic Surround (trademark) system according to which a source signal is previously subjected to an encoding processing and, when the source signal is reproduced, a 2-channel source signal is decoded to a 4-channel signal through a surround decoder. The Dolby Prologic Surround System is constructed of 5 loudspeakers of 3 channel loudspeakers of Left, Center and Right disposed in front of the listener and 1 channel, 2 loudspeakers of Left and Right disposed behind him for reproducing surround tones. As an example of the multi-channel sound system, there is a device disclosed in GB-A-2 006 583.
In a movie theater showing a 70 mm movie film, sound is reproduced from a 6-channel multi-track magnetic tape which is synchronized with the movie film. Since the magnetic tape is of a multi-track type, sound is reproduced individually from each track and, therefore, rich spacial impression can be produced while clear localization of sound is achieved.
There are variety of movie software products recorded on an optical video disc or a video tape manufactured for the purpose of playback in the home. Since sound of these movie software products is recorded in 2 channels, manufacture of a software with a surround effect requires recording of sound after reducing 6-channel multi-tracks to 2 tracks by subjecting a sound signal to the Dolby Surround encoding processing. Then, the sound signal is decoded to 4 channels of L (left), C (center), R (right) and S (surround).
An engineer producing a surround effect in a movie intends to give to a listener an effect according to which the listener feels as if he was surrounded by the sound. According to a normal arrangement of loudspeakers used for domestic purpose, however, a monaural surround output from the surround decoder is localized at the rear center due to the practical limitation that there are only 2 rear loudspeakers allotted for achieving the surround purpose. There has also been an attempt to treat this monaural surround channel by a quasi-stereophonic processing. Sufficient dimensions, however, cannot be obtained by spacial impression obtained by only the 2 rear loudspeakers and therefore a surround effect as in a 70 mm movie theater which is associated with a front screen and gives to the listener the impression that he is surrounded by the sound cannot be obtained.
It is, therefore, an object of the invention to solve the above described problem of the prior art sound field control devices and provide a sound field control device capable of realizing a surround effect as in a 70 mm movie theater.